An electronic key (a mobile device) is known in the art, for example, as disclosed in the following prior-art publications:
(1) Japanese Patent Publication No. 2007-224664(A);
(2) Japanese Patent Publication No. 2007-227246(A);
(3) Japanese Patent Publication No. 2004-134835(A);
(4) Japanese Patent Publication No. 2004-241476(A); and
(5) Japanese Patent Publication No. 2006-303327(A).
According to the known electronic key, the electronic key transmits a unique ID code of a vehicle to an in-vehicle equipment in answer to an inquiry signal from the in-vehicle equipment, so that a lockup or an unlock of a vehicle door lock is automatically authorized and/or an operation for starting up an engine is authorized when the ID code is verified. In the electronic key, for example, as disclosed in the above prior-art publications (1) to (4), a circuit board and a battery are generally accommodated in a casing, which is sealed up by a cover member. According to a structure of the electronic key of this kind, the electronic key is likely to go thick and therefore it is not easy to carry around such an electronic key. According to the above prior-art publication (5), the electronic key is formed in a card shape (hereinafter, such a key is called as a card key).
As shown in FIGS. 7 and 8, in the card key 200 of the above prior-art publication, electronic parts 202 for carrying out wireless communication with an in-vehicle equipment are mounted to a circuit board 201, wherein the electronic parts 202 and the circuit board 201 are covered by resin material 203 and molded in a plate shape. The card key 200 is manufactured by an injection molding process, according to which the resin is injected into a molding die 210, which is composed of a lower die (a core plate) 211, an upper die (a cavity plate) 212 and a slide core (a bushing) 213, as shown in FIG. 8. More in detail, the circuit board 201 is arranged on the lower die 211. Namely, a flat rear-side surface of the circuit board 201 is brought into contact with the lower die 211, while a predetermined three dimensional space is formed by the upper die 212 on a side opposite to the rear-side surface (that is, an upper side). When the slide core 213 is removed from the molding die 210, a hole extending in a lateral direction (such as, for example, a battery accommodating space) is formed.
According to the above prior-art card key 200, the three dimensional shape is formed only on the upper side thereof. Then, a surface finishing process (such as a coating, printing, or the like) is carried out for an upper-side surface. For the rear-side surface of the card key 200, a surface finishing process (the coating, the printing or the like) is carried out after a polishing process. It is a trend that a design for the card key is standardized on one hand. On the other hand, there is a strong demand in the market for facilitating the spread of the card key.